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l t URS April 30, 2007 Mr. Robert McClellon Supervisor R.E.H.S. San Joaquin County Environmental Health Department 304 East Weber Avenue,Third Floor Stockton, California 95202-2708 Subject: Quarterly Monitoring Report World Enterprises Site Stockton, California Dear Mr. McClellon: URS has prepared this letter report on behalf of RadioShack,describing the monitoring activities completed at the World Enterprises site in Stockton, California(Figure 1)during the first quarter of 2007, and summarizing the results of these monitoring activities. This report has been organized into the following sections: Background,Field Activities,Results, and Conclusions and Recommendations. BACKGROUND The World Enterprises site is located in Stockton,California.This site was operated as a debris disposal site(debris from demolished buildings,including wood,rubble,concrete, and other fill materials)under San Joaquin Local Health District Use Permits to World Enterprises from 1970 to 1978.During an annual inspection of the site on July 17,2003,the San Joaquin County Environmental Health Department(SJCEHD) staff measured methane gas concentration up to 30,000 parts per million volume (ppmV)(3 percent by volume)along the property boundary. As a result of this inspection, SJCEHD required Tandy Corporation(site owner and currently known as RadioShack)to assess whether the methane concentration along the property boundary was greater than 5 percent, and if the methane concentration along the property boundary was found to be greater than 5 percent,to implement measures for controlling methane from leaving the site. Since 2004,URS has installed 10 gas-migration monitoring probes,two vapor extraction wells, and three groundwater monitoring wells at the World Enterprises site(Figure 1)during our field investigation activities. As a result of the field investigations,methane concentrations along a portion of the property boundary were found to be above 5 percent. In September 2006, a passive soil vapor extraction trench was installed at the site to control methane from leaving the site. In December 2005, a vapor extraction pilot test was conducted to evaluate the feasibility of installing a permanent landfill gas extraction system.During this test,vapor samples were collected from the two extraction wells and analyzed for volatile organic compounds(VOCs). The analytical results for these samples showed that VOCs were present where the total VOC concentration in each of the vapor URS Corporation Crown Corporate Center 2870 Gateway Oaks Drive,Suite 150 Sacramento, CA 95833 Tel:916.679.2000 Fax: 916.679.2900 K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2007\iQ07\Monitoring Rpt.doc